git: f1b642c255a2 - main - vm_fault: Introduce a fault_status enum for internal return types
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Date: Wed, 24 Nov 2021 19:03:11 UTC
The branch main has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=f1b642c255a2931fd793219d11562310a2ce49c8
commit f1b642c255a2931fd793219d11562310a2ce49c8
Author: Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2021-11-24 18:43:26 +0000
Commit: Mark Johnston <markj@FreeBSD.org>
CommitDate: 2021-11-24 19:02:55 +0000
vm_fault: Introduce a fault_status enum for internal return types
Rather than overloading the meanings of the Mach statuses, introduce a
new set for use internally in the fault code. This makes the control
flow easier to follow and provides some extra error checking when a
fault status variable is used in a switch statement.
vm_fault_lookup() and vm_fault_relookup() continue to use Mach statuses
for now, as there isn't much benefit to converting them and they
effectively pass through a status from vm_map_lookup().
Obtained from: jeff (object_concurrency patches)
Reviewed by: kib
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D33017
---
sys/vm/vm_fault.c | 202 ++++++++++++++++++++++++++++++------------------------
1 file changed, 111 insertions(+), 91 deletions(-)
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 75868c17d32d..0e4d9fd33c6f 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -155,6 +155,19 @@ struct faultstate {
struct vnode *vp;
};
+/*
+ * Return codes for internal fault routines.
+ */
+enum fault_status {
+ FAULT_SUCCESS = 1, /* Return success to user. */
+ FAULT_FAILURE, /* Return failure to user. */
+ FAULT_CONTINUE, /* Continue faulting. */
+ FAULT_RESTART, /* Restart fault. */
+ FAULT_OUT_OF_BOUNDS, /* Invalid address for pager. */
+ FAULT_HARD, /* Performed I/O. */
+ FAULT_SOFT, /* Found valid page. */
+};
+
static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
int ahead);
static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
@@ -298,7 +311,7 @@ vm_fault_dirty(struct faultstate *fs, vm_page_t m)
/*
* Unlocks fs.first_object and fs.map on success.
*/
-static int
+static enum fault_status
vm_fault_soft_fast(struct faultstate *fs)
{
vm_page_t m, m_map;
@@ -306,17 +319,20 @@ vm_fault_soft_fast(struct faultstate *fs)
vm_page_t m_super;
int flags;
#endif
- int psind, rv;
+ int psind;
vm_offset_t vaddr;
+ enum fault_status res;
MPASS(fs->vp == NULL);
+
+ res = FAULT_SUCCESS;
vaddr = fs->vaddr;
vm_object_busy(fs->first_object);
m = vm_page_lookup(fs->first_object, fs->first_pindex);
/* A busy page can be mapped for read|execute access. */
if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 &&
vm_page_busied(m)) || !vm_page_all_valid(m)) {
- rv = KERN_FAILURE;
+ res = FAULT_FAILURE;
goto out;
}
m_map = m;
@@ -351,10 +367,12 @@ vm_fault_soft_fast(struct faultstate *fs)
}
}
#endif
- rv = pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type |
- PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind);
- if (rv != KERN_SUCCESS)
+ if (pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type |
+ PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind) !=
+ KERN_SUCCESS) {
+ res = FAULT_FAILURE;
goto out;
+ }
if (fs->m_hold != NULL) {
(*fs->m_hold) = m;
vm_page_wire(m);
@@ -368,7 +386,7 @@ vm_fault_soft_fast(struct faultstate *fs)
out:
vm_object_unbusy(fs->first_object);
- return (rv);
+ return (res);
}
static void
@@ -417,13 +435,14 @@ vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
}
}
-static int
+static enum fault_status
vm_fault_populate(struct faultstate *fs)
{
vm_offset_t vaddr;
vm_page_t m;
vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
int bdry_idx, i, npages, psind, rv;
+ enum fault_status res;
MPASS(fs->object == fs->first_object);
VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
@@ -436,6 +455,8 @@ vm_fault_populate(struct faultstate *fs)
unlock_map(fs);
unlock_vp(fs);
+ res = FAULT_SUCCESS;
+
/*
* Call the pager (driver) populate() method.
*
@@ -456,11 +477,11 @@ vm_fault_populate(struct faultstate *fs)
*/
vm_fault_restore_map_lock(fs);
if (fs->map->timestamp != fs->map_generation)
- return (KERN_RESTART);
- return (KERN_NOT_RECEIVER);
+ return (FAULT_RESTART);
+ return (FAULT_CONTINUE);
}
if (rv != VM_PAGER_OK)
- return (KERN_FAILURE); /* AKA SIGSEGV */
+ return (FAULT_FAILURE); /* AKA SIGSEGV */
/* Ensure that the driver is obeying the interface. */
MPASS(pager_first <= pager_last);
@@ -480,7 +501,7 @@ vm_fault_populate(struct faultstate *fs)
if (m != fs->m)
vm_page_xunbusy(m);
}
- return (KERN_RESTART);
+ return (FAULT_RESTART);
}
/*
@@ -510,8 +531,10 @@ vm_fault_populate(struct faultstate *fs)
PMAP_ENTER_LARGEPAGE, bdry_idx);
VM_OBJECT_WLOCK(fs->first_object);
vm_page_xunbusy(m);
- if (rv != KERN_SUCCESS)
+ if (rv != KERN_SUCCESS) {
+ res = FAULT_FAILURE;
goto out;
+ }
if ((fs->fault_flags & VM_FAULT_WIRE) != 0) {
for (i = 0; i < atop(pagesizes[bdry_idx]); i++)
vm_page_wire(m + i);
@@ -596,7 +619,7 @@ vm_fault_populate(struct faultstate *fs)
}
out:
curthread->td_ru.ru_majflt++;
- return (rv);
+ return (res);
}
static int prot_fault_translation;
@@ -699,18 +722,18 @@ vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
return (result);
}
-static int
+static enum fault_status
vm_fault_lock_vnode(struct faultstate *fs, bool objlocked)
{
struct vnode *vp;
int error, locked;
if (fs->object->type != OBJT_VNODE)
- return (KERN_SUCCESS);
+ return (FAULT_CONTINUE);
vp = fs->object->handle;
if (vp == fs->vp) {
ASSERT_VOP_LOCKED(vp, "saved vnode is not locked");
- return (KERN_SUCCESS);
+ return (FAULT_CONTINUE);
}
/*
@@ -732,7 +755,7 @@ vm_fault_lock_vnode(struct faultstate *fs, bool objlocked)
error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT);
if (error == 0) {
fs->vp = vp;
- return (KERN_SUCCESS);
+ return (FAULT_CONTINUE);
}
vhold(vp);
@@ -744,7 +767,7 @@ vm_fault_lock_vnode(struct faultstate *fs, bool objlocked)
vdrop(vp);
fs->vp = vp;
KASSERT(error == 0, ("vm_fault: vget failed %d", error));
- return (KERN_RESOURCE_SHORTAGE);
+ return (FAULT_RESTART);
}
/*
@@ -1112,33 +1135,35 @@ vm_fault_allocate_oom(struct faultstate *fs)
/*
* Allocate a page directly or via the object populate method.
*/
-static int
+static enum fault_status
vm_fault_allocate(struct faultstate *fs)
{
struct domainset *dset;
- int rv;
+ enum fault_status res;
if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) {
- rv = vm_fault_lock_vnode(fs, true);
- MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE);
- if (rv == KERN_RESOURCE_SHORTAGE)
- return (rv);
+ res = vm_fault_lock_vnode(fs, true);
+ MPASS(res == FAULT_CONTINUE || res == FAULT_RESTART);
+ if (res == FAULT_RESTART)
+ return (res);
}
- if (fs->pindex >= fs->object->size)
- return (KERN_OUT_OF_BOUNDS);
+ if (fs->pindex >= fs->object->size) {
+ unlock_and_deallocate(fs);
+ return (FAULT_OUT_OF_BOUNDS);
+ }
if (fs->object == fs->first_object &&
(fs->first_object->flags & OBJ_POPULATE) != 0 &&
fs->first_object->shadow_count == 0) {
- rv = vm_fault_populate(fs);
- switch (rv) {
- case KERN_SUCCESS:
- case KERN_FAILURE:
- case KERN_PROTECTION_FAILURE:
- case KERN_RESTART:
- return (rv);
- case KERN_NOT_RECEIVER:
+ res = vm_fault_populate(fs);
+ switch (res) {
+ case FAULT_SUCCESS:
+ case FAULT_FAILURE:
+ case FAULT_RESTART:
+ unlock_and_deallocate(fs);
+ return (res);
+ case FAULT_CONTINUE:
/*
* Pager's populate() method
* returned VM_PAGER_BAD.
@@ -1174,11 +1199,11 @@ vm_fault_allocate(struct faultstate *fs)
if (fs->m == NULL) {
if (vm_fault_allocate_oom(fs))
vm_waitpfault(dset, vm_pfault_oom_wait * hz);
- return (KERN_RESOURCE_SHORTAGE);
+ return (FAULT_RESTART);
}
fs->oom_started = false;
- return (KERN_NOT_RECEIVER);
+ return (FAULT_CONTINUE);
}
/*
@@ -1186,11 +1211,12 @@ vm_fault_allocate(struct faultstate *fs)
* that the pager has it, and potentially retrieve additional
* pages at the same time.
*/
-static int
+static enum fault_status
vm_fault_getpages(struct faultstate *fs, int *behindp, int *aheadp)
{
vm_offset_t e_end, e_start;
int ahead, behind, cluster_offset, rv;
+ enum fault_status status;
u_char behavior;
/*
@@ -1227,10 +1253,10 @@ vm_fault_getpages(struct faultstate *fs, int *behindp, int *aheadp)
*/
unlock_map(fs);
- rv = vm_fault_lock_vnode(fs, false);
- MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE);
- if (rv == KERN_RESOURCE_SHORTAGE)
- return (rv);
+ status = vm_fault_lock_vnode(fs, false);
+ MPASS(status == FAULT_CONTINUE || status == FAULT_RESTART);
+ if (status == FAULT_RESTART)
+ return (status);
KASSERT(fs->vp == NULL || !fs->map->system_map,
("vm_fault: vnode-backed object mapped by system map"));
@@ -1269,7 +1295,7 @@ vm_fault_getpages(struct faultstate *fs, int *behindp, int *aheadp)
*aheadp = ahead;
rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp);
if (rv == VM_PAGER_OK)
- return (KERN_SUCCESS);
+ return (FAULT_HARD);
if (rv == VM_PAGER_ERROR)
printf("vm_fault: pager read error, pid %d (%s)\n",
curproc->p_pid, curproc->p_comm);
@@ -1282,11 +1308,11 @@ vm_fault_getpages(struct faultstate *fs, int *behindp, int *aheadp)
VM_OBJECT_WLOCK(fs->object);
fault_page_free(&fs->m);
unlock_and_deallocate(fs);
- return (KERN_OUT_OF_BOUNDS);
+ return (FAULT_OUT_OF_BOUNDS);
}
KASSERT(rv == VM_PAGER_FAIL,
("%s: unepxected pager error %d", __func__, rv));
- return (KERN_NOT_RECEIVER);
+ return (FAULT_CONTINUE);
}
/*
@@ -1329,8 +1355,8 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
int fault_flags, vm_page_t *m_hold)
{
struct faultstate fs;
- int ahead, behind, faultcount;
- int result, rv;
+ int ahead, behind, faultcount, rv;
+ enum fault_status res;
bool dead, hardfault;
VM_CNT_INC(v_vm_faults);
@@ -1356,11 +1382,11 @@ RetryFault:
* Find the backing store object and offset into it to begin the
* search.
*/
- result = vm_fault_lookup(&fs);
- if (result != KERN_SUCCESS) {
- if (result == KERN_RESOURCE_SHORTAGE)
+ rv = vm_fault_lookup(&fs);
+ if (rv != KERN_SUCCESS) {
+ if (rv == KERN_RESOURCE_SHORTAGE)
goto RetryFault;
- return (result);
+ return (rv);
}
/*
@@ -1374,9 +1400,9 @@ RetryFault:
(fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 &&
(fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) {
VM_OBJECT_RLOCK(fs.first_object);
- rv = vm_fault_soft_fast(&fs);
- if (rv == KERN_SUCCESS)
- return (rv);
+ res = vm_fault_soft_fast(&fs);
+ if (res == FAULT_SUCCESS)
+ return (KERN_SUCCESS);
if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
VM_OBJECT_RUNLOCK(fs.first_object);
VM_OBJECT_WLOCK(fs.first_object);
@@ -1406,23 +1432,20 @@ RetryFault:
fs.pindex = fs.first_pindex;
if ((fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) != 0) {
- rv = vm_fault_allocate(&fs);
- switch (rv) {
- case KERN_RESTART:
- unlock_and_deallocate(&fs);
- /* FALLTHROUGH */
- case KERN_RESOURCE_SHORTAGE:
+ res = vm_fault_allocate(&fs);
+ switch (res) {
+ case FAULT_RESTART:
goto RetryFault;
- case KERN_SUCCESS:
- case KERN_FAILURE:
- case KERN_PROTECTION_FAILURE:
- case KERN_OUT_OF_BOUNDS:
- unlock_and_deallocate(&fs);
- return (rv);
- case KERN_NOT_RECEIVER:
+ case FAULT_SUCCESS:
+ return (KERN_SUCCESS);
+ case FAULT_FAILURE:
+ return (KERN_FAILURE);
+ case FAULT_OUT_OF_BOUNDS:
+ return (KERN_OUT_OF_BOUNDS);
+ case FAULT_CONTINUE:
break;
default:
- panic("vm_fault: Unhandled rv %d", rv);
+ panic("vm_fault: Unhandled status %d", res);
}
}
@@ -1474,23 +1497,20 @@ RetryFault:
*/
if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT ||
fs.object == fs.first_object)) {
- rv = vm_fault_allocate(&fs);
- switch (rv) {
- case KERN_RESTART:
- unlock_and_deallocate(&fs);
- /* FALLTHROUGH */
- case KERN_RESOURCE_SHORTAGE:
+ res = vm_fault_allocate(&fs);
+ switch (res) {
+ case FAULT_RESTART:
goto RetryFault;
- case KERN_SUCCESS:
- case KERN_FAILURE:
- case KERN_PROTECTION_FAILURE:
- case KERN_OUT_OF_BOUNDS:
- unlock_and_deallocate(&fs);
- return (rv);
- case KERN_NOT_RECEIVER:
+ case FAULT_SUCCESS:
+ return (KERN_SUCCESS);
+ case FAULT_FAILURE:
+ return (KERN_FAILURE);
+ case FAULT_OUT_OF_BOUNDS:
+ return (KERN_OUT_OF_BOUNDS);
+ case FAULT_CONTINUE:
break;
default:
- panic("vm_fault: Unhandled rv %d", rv);
+ panic("vm_fault: Unhandled status %d", res);
}
}
@@ -1513,16 +1533,16 @@ RetryFault:
*/
VM_OBJECT_WUNLOCK(fs.object);
- rv = vm_fault_getpages(&fs, &behind, &ahead);
- if (rv == KERN_SUCCESS) {
+ res = vm_fault_getpages(&fs, &behind, &ahead);
+ if (res == FAULT_SUCCESS) {
faultcount = behind + 1 + ahead;
hardfault = true;
break; /* break to PAGE HAS BEEN FOUND. */
}
- if (rv == KERN_RESOURCE_SHORTAGE)
+ if (res == FAULT_RESTART)
goto RetryFault;
- if (rv == KERN_OUT_OF_BOUNDS)
- return (rv);
+ if (res == FAULT_OUT_OF_BOUNDS)
+ return (KERN_OUT_OF_BOUNDS);
VM_OBJECT_WLOCK(fs.object);
}
@@ -1583,12 +1603,12 @@ RetryFault:
* lookup.
*/
if (!fs.lookup_still_valid) {
- result = vm_fault_relookup(&fs);
- if (result != KERN_SUCCESS) {
+ rv = vm_fault_relookup(&fs);
+ if (rv != KERN_SUCCESS) {
fault_deallocate(&fs);
- if (result == KERN_RESTART)
+ if (rv == KERN_RESTART)
goto RetryFault;
- return (result);
+ return (rv);
}
}
VM_OBJECT_ASSERT_UNLOCKED(fs.object);